Any good tyre (or ANY Automotive place) should be using Torque limiting bars on their rattle guns, to prevent over tightening.
Before they were available, I remember a customer ringing us from the side of the road, with a flat tyre, and he couldn't undo the nuts. It was serviced a while ago, and the nuts tent to lock up a bit after a while, but he got a tow to a wheel shop to change it for him, and sent us the bill for the tow, and swap. (Dunno what happened after that..)